With reference to food chains in ecosystems, consider the following statements: 1. A food chain illustrates the order in which a chain of organisms feed upon each other. 2. Food chains are found within the populations of a species. 3. A food chain illustrates the numbers of each organism which are eaten by others. Which of the statements given above is/are correct?

With reference to food chains in ecosystems, consider the following statements: 1. A food chain illustrates the order in which a chain of organisms feed upon each other. 2. Food chains are found within the populations of a species. 3. A food chain illustrates the numbers of each organism which are eaten by others. Which of the statements given above is/are correct? Correct Answer 1 only

The correct answer is 1 only.

Key Points

• Food Chain
  • Transfer of food energy from green plants (producers) through a series of organisms with repeated eating and being eaten link is called a food chain.
  • E.g. Grasses → Grasshopper → Frog → Snake → Hawk/Eagle.
  • Each step in the food chain is called a trophic level.
  • A food chain starts with producers and ends with top carnivores.
  • The trophic level of an organism is the position it occupies in a food chain.
  • A food chain illustrates the order in which a chain of organisms feeds upon each other.
    • Hence statement 1 is correct.
  • ​Food chains are found within the populations of a species. (Man won’t eat man – Hence statement 2 is not correct.)
  • A food chain illustrates the numbers of each organism that are eaten by others (food web illustrates the number, not the food chain).​
    • Hence statement 3 is not correct.
• Hence, option 1 is correct.

Additional Information

• Grazing food chain
  • The consumers which start the food chain, utilizing the plant or plant part as their food, constitute the grazing food chain.
  • For example, in a terrestrial ecosystem, the grass is eaten by a caterpillar, which is eaten by a lizard, and the lizard is eaten by a snake.
  • In the Aquatic ecosystem phytoplankton (primary producers) are eaten by zooplanktons which are eaten by fishes and fishes are eaten by pelicans.
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• Detritus food chain
  • This type of food chain starts from the organic matter of dead and decaying animals and plant bodies from the grazing food chain.
  • Dead organic matter or detritus feeding organisms are called detrivores or decomposers.
  • The detrivores are eaten by predators.
  • In an aquatic ecosystem, the grazing food chain is the major conduit for energy flow.
  • As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.